High power factor of metal halide lamp with dimming control

A high-power-factor high-efficiency electronic ballast for high intensity discharge lamp (HID) applications is presented in this paper. The electronic ballast consists of a boost type power factor corrected rectifier, a full bridge inverter, and a resonant tank. The power factor pre-regulator produces sinusoidal input current in phase with mains voltage. The phase-shift PWM scheme for full bridge inverter is adopted. In this control scheme, the constant switching frequency with variable duty cycle is used for dimming control. The series-resonant parallel-loaded circuit is used to drive the metal halide lamp (MHL), one of the high intensity discharge lamp. The over-voltage and over-current protection circuits are also considered in a 70 W MHL hardware prototype for safety operation. Finally, experimental results are presented to verify the characteristics of high power factor and dimming control of electronic ballast for metal halide lamp